def fun(s):
    counts = {}
    for i in s:
        counts[i] = counts.get(i, 0) + 1
        l_count = list(counts.items())
    l = []
    for i in range(0, len(l_count) - 1):
        if l_count[i][1] == 1:
            l.append(l_count[i][0])
    return ''.join(l)


print(fun(input("请输入任意字符串：")))
